Please don't flame me for being anti-S&W (I have half a dozen or so), but the truth is that they cut a few corners on the SW1911 series.
You're better off getting a gunsmith to fit a set of Infinity SV or Ed Brown ambis than getting factory SW ambis. The factory versions are MIM junk and if you use them enough it's very likely that they're going to break. Fitting ambis is easy to do and any gunsmith should be able to handle it easily. That'll save you the Fedex or UPS overnight charge that's going to run around $40-50 since it has to be overnight shipped and you can't use the post office unless you have an FFL.
I'm no gunsmith and I can fit a set of SV's in 20min or so...and you can also have them contoured to the exact width and shape that feels right (takes a little longer to do that).
Honestly, I'd avoid the issue entirely and spend the same amount of money and get a better gun from a number of other companies, but that's an entirely different discussion